An Investigation of Tradeoffs in Herbicide Resistant <i>Brassica rapa</i>: Effects on Pollen and Ovule Production, Biomass and Development

Abstract

For decades, herbicides have been used to control weeds and increase crop yields, a practice resulting in a growing number of weeds that are herbicide resistant. Like the problem of antibiotic resistance for medicine, herbicide resistant weeds present a significant agricultural challenge. To meet this challenge, we need management strategies informed by a more complete understanding of the biology of herbicide resistance. With this goal in mind we investigated tradeoffs in growth and reproduction of Atrazine Resistant (AR) versus Atrazine Susceptible (AS) Brassica rapa grown at two temperature regimes. Between the strains, tradeoffs were evident for pollen production and overall plant development. AS plants produced significantly more pollen per flower compared to AR plants. Additionally, development was significantly delayed in AR as compared to AS plants. Atrazine resistant plants took 20.5% longer than atrazine susceptible plants to produce their first true leaves, 13.0% longer to produce buds and 8% longer to produce the first flower as compared to the atrazine susceptible strain. Biomass, ovule count and pollen count were all greater in the cool treatment, however growth was significantly delayed as compared to the warm treatment. Plants in the cool treatment had significantly greater above ground biomass (26.5%) than plants in the warm treatment, but there was no effect of strain on biomass. Similarly, we found a significant effect of temperature, but not strain, on the average number of ovules produced per flower, with the warm treatment plants producing significantly fewer ovules than plants in the cool treatment. Warm temperatures also had a significant negative effect on pollen production. This study expands our understanding of tradeoffs associated with herbicide resistance to include effects on components of both male and female fitness.

Herbicide Resistant Crops and Weeds - A Review

“…Worldwide reported cases of glyphosate resistant weeds (Heap, 2021) RANI ET AL S363 ported in 1957 and since than many economically considerable weeds like-Lolium rigidum (rigid Ryegrass), Avena fatua (wild oats), Amaranthus retroflexus (redroot pigweed), Amaranthus hybridus (smooth pigweed), Setaria viridis (green foxtail) and Conyza canadensis (horseweed) etc. become herbicide resistant (Robin Bingham et al, 2017). "Resistance is a natural phenomenon which occurs spontaneously in weed populations, but is only noticed when a selection pressure is applied to the weeds via herbicide application".…”

Herbicides as anthropogenic drivers of eco‐evo feedbacks in plant communities at the agro‐ecological interface

“…Likewise, the correlated changes in traits of herbicide-resistant plants can affect their interactions with mutualists. For instance, atrazine-resistant Brassica rapa produced significantly less pollen per flower and flowered later than atrazine-susceptible plants (Bingham, King, & Keck, 2017), which could potentially affect their interactions with pollinators. Likewise, shifts in flowering time (Wang et al, 2010; Figure 4, Table S3) or traits associated with selfing (Kuester et al, 2017) can reduce availability of resources to pollinator communities leading to shifts in their visitation rates or diversity in ways that feedback on evolution of these floral traits.…”

Absence of genetic differentiation in performance traits of Sinapis arvensis populations from crop and non‐crop habitats across Northern Algeria: Implications for management

“…Florasulam acts by inhibition of ALS, blocking the synthesis of amino acids responsible for cell division in meristems, whereas the auxin-type herbicide 2,4-D acts by abnormally increasing cell wall plasticity, protein biosynthesis and ethylene production in plant tissues. Often, herbicide resistance comes with fitness costs that arise from the allocation of limiting resources away from present and future growth and reproduction or are directly caused by the mutation of the target site of the herbicide (Bingham et al, 2017). For instance, fitness costs are observed in pollen production and overall plant development of Brassica rapa atrazine-resistant versus atrazine-susceptible populations (Bingham et al, 2017), and resistant biotypes of S. arvensis to some auxinic herbicides showed significant reduction in plant height, leaf area and root length compared to susceptible biotypes (Hall and Romano, 1995).…”